Any i/o handle constructor taking a path_handle must take implementation from the path_handle

[ned14]

path_handle ought to be able to define the implementations of file_handle, directory_handle and so on. Then KV hardware can be supported by having path_handle return a file_handle which calls the SNIA KV API, or NTFS kv lookup can work if the path_handle refers to a NTFS volume, and so on.